Small electronic components such as a chip capacitor are mounted on a wiring board (semiconductor package), together with a semiconductor element (chip). Such packages have experienced generalization of high density mounting in recent years, and in particular, a semiconductor chip such as an MPU requiring a switching operation with higher speed is mounted on a package. On such a package, a large number of chip capacitors are mounted for suppressing signal transmission delays or the like caused by an increase in inductance generated in an interconnection or by capacity coupling between interconnections. Such chip capacitors also function as decoupling capacitors for stabilizing the power supply voltage by reducing crosstalk noise, switching noise and the like.
Moreover, a wiring board having a semiconductor element and chip capacitors mounted thereon has a structure in which the entire capacitors and the semiconductor element are encapsulated with a molding resin for insulating exposed conductor portions thereof from the external.
An example of such a structure is described in Patent document 1 (Japanese Laid-open Patent Publication No. 2005-236035). Another example related to the structure is described in Patent document 2 (Japanese Laid-open Patent Publication No. 2007-335740).
Chip capacitors are very small electronic components as compared with semiconductor elements. Accordingly, when such chip capacitors are mounted on a board, a gap between each of the chip capacitors and the surface of the package (board) becomes very small. As a result, when the capacitors are encapsulated with a molding resin, a void (air bubble) is likely to be generated in the resin filled in a gap between each of the capacitors and the board, in the process in which the resin flows to the inner side of the gap from the periphery portion of the gap around the capacitor (portion from which the resin is injected).
Where such a void remains without being released, an inconvenience may occur in that the capacitor causes a short circuit via the void due to aged deterioration (such as moisture invasion) during use of the product (semiconductor device). Such a problem may also occur on a package where a similar passive device such as a chip-shaped resistance element is mounted.